The long term objective of this project is to determine the unique mechanisms responsible for fetal wound healing. Wounds in the fetus heal by processes which are significantly different than those involved in adult wound healing. There is an absence of acute inflammation, contraction, and fibrosis resulting in minimal or no scar formation. The fetal tissue matrix has abundant quantities of hyaluronan which is thought to be one of the critical factors responsible for the optimal fetal wound healing response. This proposal will define the mechanisms whereby hyaluronan modulates extracellular matrix deposition by dermal fibroblasts. This will include measuring the effects of hyaluronan on the expression of collagen types I and III, fibronectin, matrix metalloproteinases, hyaluronan and its receptors. Rates of protein synthesis will be quantified by gel electrophoresis and autoradiography of pulse-labeled proteins. Functional activity of the matrix metalloproteinases (collagenases and gelatenases) will be determined using a radiolabeled collagen substrate assay developed in the investigators laboratory. In addition, this proposal will also define the signal transduction mechanism whereby hyaluronan modulates matrix gene expression. Expression of hyaluronan receptors will be determined by quantitation at the RNA and protein levels. Assays determining the ability of hyaluronan receptors to bind to ligand will also be used. Signaling pathways will be identified by measuring protein phosphorylation in the presence or absence of pathway-specific inhibitors. These studies will focus on normal dermal and wound fibroblasts isolated from both fetal and adult rabbits. In addition, specific studies are designed to test the observations made in cell culture to in vivo findings in fetal and adult rabbits. The in vivo studies will employ in situ hybridization for transcript analysis and protein expression will be accomplished using immunohistochemistry. Information generated by these studies will provide a better understanding of fetal physiology and development. This basic biological information will lead to better clinical rationales for treating the many human wound healing problems such as keloid, hypertrophic burn scar contractures, peritoneal adhesions and strictures as well as chronic non-healing wounds such as pressure, diabetic, and venous stasis ulcers. These clinical problems result in major morbidity and health care costs.